Wave power plant

ABSTRACT

The invention relates to a wave power plant, comprising a floating body ( 1 ) and means for converting the wave energy received by the body into electric power. The front side of the cross-section of the body ( 1 ) opposite to the main incoming direction (A) of the waves is designed to slant forward and upwards in its upper part ( 11 ) and to slant backwards and downwards in its lower part ( 12 ), in such a way that the propagating wave meets the upper and lower part wave at different stages, whereby the lower part tends to move mainly in the opposite direction with respect to the upper part.

The present invention relates to a wave power plant, comprising a floating body and means for converting the wave energy received by the body into electric power.

The aim of the present invention is to provide an improved wave power plant by means of which the output of the wave power plant can be increased and its operational preconditions in varying wave conditions can be improved.

To achieve this aim, the wave power plant according to the present invention is characterised in that the body is a mainly vertical wall, which is for the most part below the water level W, but with its upper part above the water level, and the front side of the cross-section of the body opposite to the main incoming direction of the waves is designed to slant forward and upwards in its upper part and to slant backwards and downwards in its lower part, in such a way that the propagating wave meets the upper and lower part wave at different stages, whereby the lower part tends to move mainly in the opposite direction with respect to the upper part. The body forms a gently sloping letter S in cross-section, where the end parts of the S settle in a basically horizontal position. In this connection, the terms vertical and horizontal refer to the position of the body in a state where the body is essentially stationary in calm water. When in operation, the body is on average inclined in the incoming direction of the waves.

The body of the wave power plant is preferably dimensioned in such a way that its draught is 0.5× the length of the smallest functional wave desired. The upper surface of the body is preferably closed and even.

In the solution according to the invention, the forces and movements are opposite in the upper and lower part of the device, thus generating a large movement and high force used further to produce electric power, for example by means of a rotator/gyratory generator, which is rotated by utilising gravitation and gyro force. From the publications EP 1 384 824 B1 and WO2005/071257 A1 is known a solution in which the moment of momentum of the rotation of the gyro is used to generate the torque of the rotator when the gyro shaft is rolled by means of the waves. The problem with these known wave power plants is that the torque enhancing the rotation of the rotator shaft is received on it only for a short time, twice during a full rotation of the rotator, whereas at the intermediate stages, when the gyro shaft turns, the moment of the momentum of the rotation of the gyro generates a torque which inclines the body. If the body is able to incline in the direction of the torque, it will perform unnecessary work and brake the rotation of the rotator. It is thus difficult to make the rotator rotate in step with the waves.

The invention is described in greater detail in the following, with reference to the accompanying drawings, in which:

FIG. 1 shows a diagrammatic oblique front view of the body of the wave power plant according to one embodiment of the invention;

FIG. 2 shows an oblique rear view of the body according to FIG. 1, and

FIG. 3 shows a diagrammatic view in principle of an implementation of power plant units positioned in the body.

FIGS. 1 to 2 show a diagrammatic view in principle of a preferred embodiment of the body 1 of the wave power plant. The body 1 is a wall which is mainly vertical, or when in operation, inclined on average in the incoming direction of the wave, and which is for the most part below the water level W, but with its upper part above the water level. The wall-type shape and mainly vertical or inclined position of the body converts the flow energy of the waves into kinetic energy of the body efficiently and over a large surface area. The draught of the body 1 is preferably dimensioned to correspond to 0.5× the length of the smallest functional wave desired, thus equalling the movement of the said wave in the vertical direction. In the exemplary implementation according to the Figures, the upper part 11 of the front side of the body 1 opposite to the main incoming direction A of the waves is designed to curve forward and the lower part 12 to curve backwards, thus forming a gently sloping letter S in cross-section, in such a way that the propagating wave meets the upper and lower part wave at different stages, whereby as the wave propagates, the upper end and lower end of the device are mostly at different stages of the wave. In these areas are then generated forces and movement in opposite directions due to buoyancy and the kinetic movement (flow) of the wave. In a small wave, there is practically no wave motion in the lower part of the device, whereupon the stationary water resists the movement of this part. The purpose of the design of the upper part is that the variation in buoyancy caused by the vertical movement of the wave together with the pressure variation caused by the kinetic movement will move it in stages in different directions: up, to the rear, down and to the front. When the lower part is in contact with a part of a wave which is at least mostly at a different stage, the force generated by this kinetic pressure change (flow) moves it mainly in the opposite direction compared to the upper part. The upper surface 16 of the body 1 is made closed.

Reference numeral 13 designates the location of a power plant unit described in greater detail, for example, in connection with FIG. 3, of which units there are two in the embodiment shown. The anchoring is preferably fixed to a low-movement position 33 on the lower part of the device, whereby the anchor forces and movements are easy to control. The anchor force participates in bringing about the movement of the body/generating the force and its energy is recovered. In the example case, the anchoring is implemented with weights 30 suspended below the device. In connection with the weights are arranged transversely extending elongated anchoring means 31 which are connected to the bottom of the installation site of the wave power plant. The weights give the anchoring flexibility and form a lower pivot 32 for the system in big waves. In small waves, the pivot is at the anchoring attachment point 33 on the body. With this arrangement, the system adjusts to the energies generated by waves of different sizes. The movements in the system are very small and also the variations in force remain moderate. In addition to the spherical shape shown in the Figures, the weights of the anchoring may also have, for example, a flat or disciform shape, which enhances the utilisation of the anchor force in creating movement and producing energy.

The anchoring weights 30 are preferably hollow, for example, filled partly with concrete and partly with air, whereby they float during transport. When the cavity is filled with water, the weights sink and at the same time pull the floating power plant into the correct position. When the device is removed, the cavities of the weights are filled with air, whereby they will again float to facilitate transport. The power plant itself will then also rise close to the surface, into a horizontal position, in which case the draught is small, thus facilitating, for example, docking. The anchor forces are utilised in energy production. The force is mainly opposite to the direction of movement (force) of the upper front part of the body, whereby it enhances energy production for its part.

The interface of the electric cable (not shown) with the body is preferably also located in a low-movement position in the vicinity of the anchoring point and led to the bottom of the sea following the anchor lines to minimise movements, where its wear is slight. The device may be made large because its width is selectable. The output is as high as several megawatts, the irregularity of the wave forming a certain limit to the width of the body. The height of the device may be, for example, within the range from 10 to 40 m, preferably about 15 to 25 m, and the length, for example, within the range from 30 to 100 m, preferably about 50 to 75 m. These are only examples of the dimensions of the device describing its order of magnitude for making high power output possible. A large size is possible because the forces are converted into electric power inside a closed body.

The counterforce of the wave force in generating the torque is gravitation and gyro force. Gravitation and gyro force alternate and occur simultaneously. The forces used to produce electricity (gravitational force, gyro force and variable acceleration in different directions generated by the wave motion) are internal to the closed body. This makes possible a simple mechanism which is protected from the marine atmosphere and sea water. There are no moving mechanisms outside the closed body.

The dimensions of the device in elevation and in the lateral direction are large compared to the size of the wave, whereby the opposite stages in the wave can be utilised. The device utilises simultaneously the changing buoyancy and the kinetic energy of the wave in all directions.

The device preferably has a beaching ramp for safely receiving a service boat. Backwards from the upper part of the ramp extends a floating rope which is used via a winch to facilitate beaching. On the incoming direction side of the wave, in front of the ramp, is a shield 34 through which a service entrance is provided.

In one preferred embodiment, in the lower part of the body is provided a water tank 14, by means of which the floating position can be adjusted.

When transported to the site, the tank is empty and the device floats on its face and low. The water tank 14 may have a round cross-section, its axis being horizontal in the longitudinal direction, that is, perpendicular to the direction of propagation of the wave. In this way it will not form significant inertia or use energy. When the device rolls with the wave, the water in the tank will not follow to any significant degree.

The fringe side of the middle section of the body is convex and designed in such a way that when the device moves with the wave, the rear side will not “form” a wave, that is, it will not transfer energy back to the water. The end areas of the body are flat, thus utilising the suction of the wave circulating the device. This enlarges the capture width.

The system according to the present invention adapts as a whole to the motions of waves of different sizes so that the system will not have to resist the high forces of wave motions.

In the embodiment shown in FIG. 3, the wave power plant comprises an elongated floating body 1 which rolls to and fro around the elongated roll axis B of the body. The incoming direction A of the waves is perpendicular to the roll axis B of the body 1. The body 1, therefore, rolls to and fro with respect to one axis B. On the body are positioned two or more power plant units which convert wave energy into electricity. Both power plant units comprise a rotator 3 which rotates on average around a mainly vertical rotator shaft 2. The rotator 3 comprises a gyro 5 which rotates on average around a mainly horizontal gyro shaft 4. The gyro 5 and the gyro shaft 4 rotate around the rotator shaft 2 with the rotator 3. The generator 6 is connected to rotate together with the gyro. The rotator 3 comprises a mass M, the centre of gravity of which is at a distance from the rotator shaft 2, whereupon when the body inclines, the mass M and gyro 5 alternately generate a parallel torque on the rotator 3, as described in greater detail below. The mass M is connected to the rotator shaft 2 with an arm 10 essentially parallel to the axis of rotation 4 of the gyro. The gyro 5 and the generator 6 form the dead mass M partly or completely.

The generator 6 is located on the gyro shaft 4 or connected to be driven by the gyro shaft. The outer end of the rotator 3, which is far from the rotator shaft 2, is provided with a small wheel 8 on which the outer end of the rotator rests and which rotates without sliding along a circular track 9 which surrounds the rotator shaft 2 coaxially. The wheel 8, the gyro 5 and the generator 6 are connected to rotate together. They may be on the same shaft or connected with appropriate transmission ratios to one another. In this embodiment, the speed of rotation of the gyro is constant with respect to the speed of rotation of the rotator 3 around the rotator shaft 2 and correspondingly constant with respect to the period of the waves. In this embodiment, only one generator 6 is required in each power plant unit. The gyro 5 and the generator 6 may be located close to the outer end of the rotator, whereby they form an essential part of the mass M which rotates the rotator on the basis of gravity, when the mass attempts to move in the direction in which the body is inclined. The moment of momentum of the rotating gyro 5 also generates a torque enhancing the rotation of the rotator 3 when the rolling of the body 1 turns the gyro shaft 4, whereupon the precession force generates a torque in the rotator, the direction of which is at a 90 degree angle to the direction of turning. The direction of rotation of the gyro must be such that the gyro, as it were, rotates/advances in the direction of rotation of the rotator.

When the angle of inclination of the body 1 is at its largest and its rolling direction turns, the rotator preferably has the direction shown in FIG. 3, which is the same as the direction of the roll axis B. In this case, the angle between the direction of the rotator and direction of inclination of the body, that is, the so-called phase lag is 90 degrees. In other words, the rotator is at a 90 degree lag (behind) with respect to the inclination of the body. The mass M then gives the best torque due to the effect of gravity. The gyro 5, on the other hand, does not affect the torque of the rotator 3 on the track 9 plane at this stage, because the roll axis B and the gyro shaft 4 are parallel. When the rotator 3 continues to rotate towards the direction in which the gyro shaft 4 is perpendicular to the roll axis B, the rolling motion turns the gyro shaft increasingly faster. The change of direction of the gyro shaft 4 is at its fastest when the shaft 4 is perpendicular to the roll axis B, whereupon the moment of the gyro force pushes the rotator with its maximum force in the direction of the track 9. The rolling motion of the body is then at its fastest and the plane of the track is essentially horizontal. In that case, the mass M does not increase the torque. The torques of the gyro force and the mass, therefore, alternate at 90 degree angular intervals and are, respectively, at their maximum at angular intervals of 180 degrees, that is, both twice during one revolution of the rotator.

The most powerful operation is thus achieved when the said phase lag is adjusted to 90 degrees. In the intermediate forms, the moment produced by the mass and the moment produced by the gyro on the rotator is proportional to the sine of the phase lag. The phase lag can be adjusted by adjusting the generator 6 load. In the operation of the wave power plant, its output can be adapted to the output of the wave available by varying the phase lag between 0 to 90 degrees, and in addition by adjusting the speed of rotation of the gyro.

The vertical axis of the rotator/gyro generator can be placed slightly inclined in the incoming direction of the wave, whereby the accelerations of the up-and-down motion caused by the wave take part in generating the torque.

The means for converting the wave energy received by the body into electric power are preferably located in the lower rear part of the body, in the vicinity of the roll axis. An alternative location for these means is in the upper part of the body, whereupon in addition to the said gravitational force and gyro force, the accelerations complying with the rolling of the body produce an additional moment on the rotator. 

1. A wave power plant, comprising a floating body and means for converting the wave energy received by the body into electric power, wherein the body is a mainly vertical wall, which configured so that, in use, it is for the most part below the water level, but with its upper part above the water level, and the front side of the cross-section of the body opposite to the main incoming direction of the waves is designed to slant forward and upwards in its upper part and to slant backwards and downwards in its lower part, in such a way that the propagating wave meets the upper and lower part wave at different stages, whereby the lower part tends, in use, to move mainly in the opposite direction with respect to the upper part.
 2. A wave power plant as claimed in claim 1, wherein the said front side is designed into a gently sloping shape, generally like a letter S.
 3. A wave power plant as claimed in claim 1, wherein the means for converting the wave energy received by the body into electric power are located inside the frame part as a closed structure.
 4. A wave power plant as claimed in claim 3, wherein the means for converting the wave energy received by the body into electric power are located in the lower rear part of the body, in the vicinity of a roll axis.
 5. A wave power plant as claimed in claim 1, wherein the wave power plant comprises anchoring arranged in the lower part of the body, the anchoring including an anchoring mass suspended on a downwards extending elongated anchoring device, in connection with which anchoring mass are arranged transversely extending elongated anchoring devices which are connected to the bottom of the installation site of the wave power plant.
 6. A wave power plant as claimed in claim 1, wherein the upper surface of the body is made essentially even.
 7. A wave power plant as claimed in claim 1, wherein the body has a draught dimensioned to correspond to 0.5× the length of the smallest functional wave desired.
 8. A wave power plant as claimed in claim 1, wherein in the lower part of the body is provided a water tank for adjusting the floating position of the wave power plant as desired.
 9. A wave power plant as claimed in claim 8, wherein the water tank is a generally cylindrical container extending in the lateral direction of the body.
 10. A wave power plant as claimed in claim 1, wherein the means for converting the wave energy received by the body into electric power comprise a rotator, which is supported on the body and rotates around an on average vertical rotator shaft, a gyro, which rotates around an on average horizontal gyro shaft, the gyro and the gyro shaft rotating around the rotator shaft with the rotator, and at least one generator, which is connected to rotate together with the gyro or the rotator, and that the rotator comprises a mass, the centre of gravity of which is at a distance from the rotator shaft, whereupon when the body rolls, the mass and gyro alternately generate a parallel torque to rotate the rotator. 